The present invention relates to acoustic echo cancellation systems and methods. More particularly, the present invention relates to acoustic echo cancellation systems and methods that employ adaptive filters to estimate the channel from the speaker to the microphone of a device. In addition, a low-frequency band is used to detect near-end voice captured by the microphone.
Double Talk Detection (DTD) is a central problem in Acoustic Echo Cancellation (AEC) systems. The AEC system uses an adaptive filter to estimate the channel from the speaker to the microphone of the device. When the channel estimate is accurate, the system can cancel the echo from the speaker at the microphone. Double talk is a term used to identify a condition where both the device speaker and the near-end user are active at the same time. AEC systems must detect double talk and stop filter adaptation while it is occurring, or stop filter adaption responsive to near-end voice detection, which is always present during double talk.
Furthermore, many AEC systems will squelch the signal from the microphone when the device speaker is active, and the near-end user is inactive. Typically squelching will stop when double-talk is detected, allowing the near-end voice to be transmitted through the system. If the DTD is inaccurate, the squelch will occur at inopportune times. This could result in excessive residual echo or missed voice content.